Conventionally, in casting a cast product, molten steel is made to flow into a mold from a runner which is communicated with the mold and, after completion of casting, the runner is removed from the cast product and the separated runner is melted again by an electric furnace and is recycled.
However, the separated runners have a complicated branched shape and hence, when the runners are directly cast into the electric furnace with profiles thereof maintained as it is, the complicated shapes are overlapped or are entangled thus increasing a total capacity of the runners. Accordingly, it is not possible to cast an amount of runners which can sufficiently fill or fully occupy a capacity of the inside of the electric furnace and hence, a so-called yielding rate is lowered thus deteriorating a melting recovery efficiency of the runners.
Accordingly, it is necessary to preliminarily crush the casting runner before charging the casting runner into the electric furnace. A hydraulic crusher has been used for this end.
The crusher is constituted of a receiving blade, a pushing blade and a hydraulic device which drives the pushing blade. By introducing a broken runner having a complicated shape between both blades, the runner is crushed due to a clamping force generated by both blades (see patent document 1).
Patent document 1: Japanese Laid-open Patent Hei6(1994)-106083.
Here, it is often the case with such a crusher that the runner which is crushed due to clamping by the receiving blade and the pushing blade sticks to a blade base body. Accordingly, even when the receiving blade and the pushing blade are separated from each other after crushing the runner, it is difficult to recover runner pieces which are finely crushed. Further, an engaging shape of the receiving blade and the pushing blade adopts a simple cutting scissors-like shape and hence, it is not always possible to form the crushed runner pieces into a finely-crushed shape whereby there has been a drawback that desired finely-crushed runners suitable for melting in the electric furnace cannot be obtained.